V~stibular Rehabilitation: Critical Decision Analysis

V~stibular Rehabilitation: Critical Decision Analysis Richard E. Gans, Ph.D., FAAA, ABSTRACT Vestibular Rehabilitation Therapy (VRT) is used by audiologists, physical and occupational therapists, and physicians as an efficacious treatment and management strategy for patients with noncompensated vestibular dysfunction secondary to a vestibular disease or disorder. Although vestibular rehabilitation techniques were first reported over a half-century ago, it has been in the past decade that these techniques have become a widdy accepted nonmedical or nonsurgical treatment strategy for patients with chronic and often debilitating symptoms. The use of diagnosis-based strategies or individualized and programmatic therapy protocols and programs has been documented as providing the best treatment outcomes. Critical decision analysis and clinical pathways provide a straightforward method for clinicians in the identification and treatment of this population. KEYWORDS: Vestibular, vestibulopathy, noncompensated, stabilized, unilateral vestibular dysfunction, vestibular rehabilitation Leaming Outcomes: Upon completion of this article, the reader will be able to (1) state the primary causes and disease processes of vestibular dysfunction, (2) describe the physiological characteristics of noncompensated vestibulopathy, and (3) list the physiological theories for vestibular rehabilitation and its appropriate application. According to the National Institutes of Health (NIH), 1 patients' complaints of dizziness and vertigo will account for nearly 7 million doctor visits. Vestibular disorders will account for 85% of these symptoms. 2 The vestibular system is subject to insult, trauma, and disease (Table 1). The disorder or disease process may cause the vestibular system to suffer a reduction or loss of function in one or both systems. The damage or change may occur either as a loss of sensory receptors within the end organ, or within the nerve itsel The sudden loss or reduction of function unilaterally will typically produce debilitating vertigo with associated autonomic and parasympathetic nervous system responses of nausea, emesis, Vestibular Diagnosis and Rehabilitation: Science and Clinical Applications; Editor in Chief, Catherine V. Palmer, Ph.D.; Guest Editor, Richard E. Gans, Ph.D., FAAA. Seminars in Hearing, volume 23, number 2, 2002. Address for correspondence and reprint requests: Richard E. Gans, Ph.D., The American Institute ofbalance, 11290 Park Boulevard, Seminole, FL 33772. E-mail: rgans@dizzy.com. 1The American Institute of Balance, Seminole, Florida. Copyright 2002 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: + 1(212) 584-4662. 00734-0451,p;2002,23,02,149,160,ftx,en;sih00208x. 149

150 SEMINARS IN HEARING/VOLUME 23, NUMBER 2 2002 Table 1 Common Causes of Unilateral Vestibular Dysfunction Autoimmune disorders Labyrinthitis Labyrinthine concussion Labyrinthine ischemia Meniere's disease Ramsey Hunt syndrome Vestibular migraine Vestibular neuritis and diaphoresis. This is similar to what occurs in acute motion sickness. Fortunately, the acute phase of most conditions will pass within hours. Other conditions, however, may linger for days, weeks, or-as in the case of Meniere's-be problematic for years. During the acute phase of the condition, the patient will require medical and pharmacological management. Patients usually wish to stay quiet and immobilized until they recover their homeostasis and manage to move about. STATUS OF THE VESTIBULAR DYSFUNCTION Patients with vestibular disorders may have had insult or damage to either the peripheral (labyrinth part of the inner ear) or central (brainstem or cerebellum) portions of the vestibular mechanism. Common inner ear disorders that cause vestibular dysfunction include labyrinthitis, vestibular neuritis, herpes zoster oticus (shingles), vestibular migraine, labyrinthine ischemia, and Meniere's disease. Many of these patients may have had only a relatively short phase of acute vertigo, or have postsurgery treatment of intractable inner ear disease such as Meniere's disease. Once out of the acute phase, they may be left with chronic symptoms affecting their sense of spatial orientation, gaze stabilization, or balance. Vestibular disorders affect two output modalities-the vestibulo-ocular reflex (VOR) that controls eye movement and gaze stabilization during active head movement, and the vestibulo-spinal reflex (VSR) that influences postural stability, translated through the mus- Table 2 Common Causes of Bilateral Vestibular Dysfunction Aminoglysides Arteriosclerosis Diabetes Microvascular disease culoskeletal system and antigravity muscles. Patients with vestibular disorders may present with defects in one or both symptoms of gaze stabilization problems or unsteadiness, usually when challenged by uneven surfaces, quick turns or with reduced vision. For those with slow, insidious vestibular changes that culminate over years, patients will not experience vertigo, but rather a loss of equilibrium and increased unsteadiness with ambulation. This often occurs in the older adult or those with a variety of nonvestibular or nonotologic related disease processes (Table 2). Individuals who have had bilateral vestibular losses secondary to aminoglyside toxicity usually present with an associated complaint of oscillopsia during head movement. VRT is a highly effective management strategy for those patients who have chronic symptoms related to a labyrinthine event.3 In order to provide the most efficacious treatment possible, the clinician will benefit by following a critical decision analysis. The first step is to understand the status of the disorder that has caused the patient's condition. Prior to the referral for, and undertaking of VRT, it will be necessary to properly define and categorize the status of the vestibular involvement. The ideal candidate for VRT will be a patient with stabilized but noncompensated unilateral vestibular dysfunction (UVD). STABILIZED VS. NONSTABILIZED A stabilized condition can best be described as one that is no longer producing attacks or episodes of debilitating vertigo and other otologic or parasympathetic responses, such as acute nausea, emesis, etc. This has been described as the labyrinthine storm. Most conditions, such as vestibular neuritis or labyrinthitis, become

VESTIBULAR REHABILITATION/GANS 151 stabilized once the acute phase has passed. The anatomical and physiological damage to the system is typically caused either by a viral or bacterial infection of the labyrinthine fluids, or a viral/bacterial inflammation of the vestibular portion of CN VIII. The patient may have symptoms related to the chronic VOR dysfunction, but no longer is subject to attacks. Meniere's disease is perhaps the best example of a chronic nonstabilized vestibular disease that may persist in an active or agitated state for years. Another example of a nonstabilized disease would be a nonoperable acoustic neuroma, or vestibular schwannoma. Because BPPV is caused by a biomechanical phenomenon rather than a neurophysiological state, it does not fit into the categorization of a stabilized vs. nonstabilized type lesion. COMPENSATED VS. NONCOMPENSATED The central nervous system (CNS) will, within days, weeks, or months, see the asymmetrical labyrinthine function and, without any external help, will reset or retune the VOR function. Central compensation is believed to occur through the plasticity of the CNS within the brainstem and cerebellum. It has been described as a neurophysiological motor re-learning phenomenon and has been documented in the literature with animal and human models. 4,5 Patients who have a spontaneous recovery of the VOR function subsequent to an acute vestibulopathy are considered to have a compensated lesion. Although these patients will continue to present with abnormal findings (i.e., reduced labyrinthine reactivity or caloric weakness on a VNG/ENG caloric), they will have no subjective report or hallucination, or exaggerated sense of motion, oscillopsia, or visually provoked symptoms. On tests of VOR function such as Vestibular Autorotation Testing, patients will present with normal gain and phase, just as if they were otherwise normal. Tests of dynamic visual acuity will appear normal, despite the caloric weakness. The caveat to clinicians is that just because there is a reduced labyrinthine reactivity, it does not mean that it is the origin of the patient's complaints. Likewise, patients may have normal caloric responses either because the horizontal canal was not involved, or the problem is in the higher frequency sensitivity of the system. The caloric test evaluates only the ultra low frequency sensitivity of the horizontal semicircular canal. (See the article in this issue by O'Leary for more information on the limitations of caloric testing.) IDENTIFYING VRT CANDIDATES Patients who find their everyday function is adversely affected or limited by this stabilized, but noncompensated asymmetry in vestibular function, may benefit from VRT. The vestibulopathy may affect the full range of acceleration, or frequency, or just regions of acceleration, similar to a frequency-specific hearing loss within the cochlea. Likewise, the direction of the acceleration also may be involved. Typically, the patient's symptoms will be more provoked with acceleration toward the involved or impaired labyrinth. The manifestation of a vestibulopathy will often result in a VOR deficiency. The VORis responsible for stabilizing eye/head position at frequencies starting at about 1.5 Hz. The errors that occur in the VOR function may affect the gain or accuracy and the phase or timing of the reflex. Correct VOR function is dependent on the brain's ability to correctly signal the extraocular eye muscles to correspond their response with the initiating head movement. The hydromechanical movement of the fluid within the semicircular canals initiates this signal. The inability of the eyes to be correctly positioned with active head movement causes a retinal slippage that results in an oscillopsia. The image to be viewed appears to jump or jiggle. It may be restricted to the plane of the involvement. The extraocular eye muscles are correlated with the specific plane of the balance canals. VRT consists of systematic repetitive exercises and protocols that extinguish, or ameliorate patients' motion-provoked symptoms, as well as enhance postural stability and equilibrium. VRT is not new; it has reached its half-century mark. In the 1940s, Cawthorne6

152 SEMINARS IN HEARING/VOLUME 23, NUMBER 2 2002 and Cooksey7 discussed the benefit of active eye and head movement exercise for patients who experienced labyrinthine problems. Since then, research and clinical experience has greatly advanced the scientifi.c application of this treatment methodology.b-12 Table 3 Subjective Handicap Instruments Dizziness Handicap lnventory17 Health Survey Ouestionnaire-SF-361 B Meniere's Disease-Patient Oriented Subjective lmprovement19 Vestibular Disorder Activities of Daily Living Scale2o Activities-Specific Balance Confidence Scale21 CLINICAL CORRELATES Patient evaluation may include a variety of assessment tools that are specific to revealing VOR abnormalities. This may include tests of gaze stabilization and visual acuity with active head movement. Tests of VSR function, such as Computerized Dynamic Posturography (CDP),13 or simple modified Clinical Test of Sensory Integration of Balance (CTSIB)14 may reveal UVD patterns. Traditionally performed tests, such as VNG/ENG calories, or less commonly performed rotary chair, may not reveal a high frequency UVD. Patients who experience VOR problems at a higher frequency can often be identified with tests that disrupt visual acuity during active head movement, or that quantify the VOR gain and phase.15,16 Recent investigation and reports of gaze stabilization tests17 hold significant promise in simple and straightforward analysis of VOR function beyond what is currently available. All too often, patients with undetected UVDs whose history and symptoms strongly correlate with a stabilized, but noncompensated UVDs are dismissed as being a nonvestibular patient as a result of an unremarkable caloric or VNG/ENG study. SUBJECTIVE HANDICAP SCALES AND PATIENT REPORT Patient rating scales have been used to identify and quantify the functional disability created by physical ailment or illness. Disease or activity-specific and global health status patient handicap scales provide a valuable resource for establishing baseline, as well as serial or outcome measures. Table 317-21 provides several scales used and clinically documented in the literaturep-23 These may provide excellent in- sight for clinicians in determining candidates for VRT or for those who may require further testing. PHYSIOLOGICAL BASIS OF VRT The underlying physiological basis for VRT is the plasticity of the central nervous system. VRT does not actually involve a regeneration or treatment of the damaged vestibular end organ itsel Instead, it works by allowing the central nervous system and the brain to acclimate or adapt to asymmetrical/conflicting input from the two vestibular systems. Possible mechanisms include the spontaneous rebalancing of the tonic activity within the vestibular nuclei, recovery of the VOR through adaptation, and the habituation effect that is a lessening of response to the same stimuli over time. Theoretically, central compensation should occur within 90 days following dysfunction or loss of one of the vestibular systems. Many lesions, particularly those that occur with rapid onset, do not benefit from this compensation phenomenon. Complicating or delaying the phenomenon of central compensation is the reluctance of the patient to perform any of those activities involving active head motion that produce symptoms of dizziness. This may be a primary factor as to why central compensation does not occur in many individuals. Other complicating factors include commonly prescribed drugs such as meclizine, Antivert, Valium, and other pharmaceuticals that suppress either peripheral vestibular or CNS function. These drugs will delay or prevent the central nervous system from relearning or adapting to asymmetrical sensory input. Unfortunately, the dizzy patient,

VESTIBULAR REHABILITATION/GANS 153 in his/her heightened state of anxiety about becoming dizzy (especially while at work or driving), becomes reliant on those pharmaceuticals that assist in suppressing their symptoms. VRT works best when it is used with individuals who are outside of the acute phase of a condition. The patient who is in the midst of a labyrinthine storm secondary to labyrinthitis, vestibular neuritis, or active Meniere's disease will receive little or no benefit from VRT. Most patients, however, will be in a stabilized condition. These patients present symptoms that are provoked with active head movement, often at a particular frequency of motion and in a particular direction. For example, there may be an inability to ride down a particular street where there appears to be numerous telephone poles when the patient looks out of the side window. It is common for patients to express a sensation of motion sickness while they are looking at certain patterns of floor tiles or wall coverings. One of the most common patient complaints is difficulty walking down an aisle of a grocery store while turning their head from side-toside and up-and-down while shopping. DIAGNOSIS-BASED STRATEGIES Gans,23 Shepard,24 Black,25 and Cohen,26 as well as others have supported and promoted the use of specific rehabilitation strategies correlating with specific underlying categorization of functional disability. Many wellmeaning practitioners continue to use the 50- year-old Cawthorne and 30-year-old Brandt exercises for dizzy patients, regardless of the patient's diagnosis or condition. Clinical experience and the literature strongly indicate that the success of vestibular rehabilitation is related to applying the correct treatment methodology to the appropriate corresponding dysfunction. Table 4 identifies those appropriate treatment methodologies with their corresponding functional components. Diagnosis Based Strategies as an individualized or customized therapeutic approach have been shown to produce successful outcomes.27 These strategies link the underlying physiological changes that occurred due to the disease or insult with the patient's functional symptoms. There are three approaches to therapy: adaptation, substitution, and canalith Table4 Diagnosis-Based Strategies Diagnostic Category Symptoms Strategy Objective Unilateral vestibular Disrupted gaze stabilization with Adaptation Return normaivorfunction. dysfunction, high active head movement. Extinguish symptoms. frequency May also be visually provoked. Unilateral vestibular Motion or positionally provoked Adaptation Extinguish or ameliorate dysfunction, no sense of dizziness or motion or visually provoked balance component exaggeration of motion. symptoms. Enhance VOR function. Unilateral vestibular Same as above, with addition Adaptation Same objectives as above dysfunction with of imbalance and unsteadiness and with the addition of balance when walking, particularly on substitution improved stability and component dynamic surfaces. equilibrium. Reduce visual and surface dependence. Bilateral vestibular Surface and visual dependence. Substitution, Enhance balance function. dysfunction May present with oscillopsia, if conditioning, Strengthen remaining post aminoglycoside. fall prevention sensory systems. Increase strategies. independent ambulation, reduce oscillopsia.

154 SEMINARS IN HEARING/VOLUME 23, NUMBER 2 2002 repositioning-liberatory maneuvers. They may be used independently or in conjunction with one another, depending on the patient's needs. Adaptation will reset or retune the VOR by repetitive activities. These activities will include those situations or movements that provoke the very symptoms the patient has been trying to avoid. Activities will incorporate mostly coordinated head and eye movement, along with head and eye movement with full ambulation. Presenting the patient with multiple simultaneous acceleration stimuli in a variety of planes will provide an excellent activity with a minimum of space, cost, and equipment. A good example of this would be to have the patient sit on a balance ball, with a slight bounce while they turn their head from sideto-side and read two separate word lists, such as a grocery list. Activities that disrupt the predictability of gaze stabilization or somatosensory input will be useful. Gaze stabilization exercises may progress from easy to more difficult as a progression from the patient performing Figure 1 A VRT Patient's other sensory modalities are challenged to strengthen vestibular function. side-to-side head turns while seated on a stationary chair to those while seated on a ball. Baseline, serial, or final performance can be evaluated with any technique that evaluates the VOR function. This may be as simple as testing dynamic visual acuity with a Snellen eye chart, or as complicated as using the technologically advanced Vestibular Autorotation Testing that provides a computerized analysis of the eye and head velocity. Substitution protocols will strengthen the weakened systems by reducing the dependence on the remaining ones. Or, in the case where a sensory modality is missing, will work to strengthen or make the remaining systems more trustworthy. Figure 1 is a good example of a substitution protocol application. A patient with a weakened vestibular system is forced to make it more dominant by reducing or challenging the somatosensory input by standing on a trampoline. The visual sense could be further disrupted or diminished by having the patient close his eyes or watch a moving visual stimulus while maintaining his balance. Evaluation of a patient's performance may include tests of postural stability with dynamic surface and absent vision. A simple version of this test is Horak and Schumway-Cook's classic Clinical Test of Sensory Integration ofbalance (CTSIB). A more complex test would consist of the Equitest Computerized Dynamic Posturography, used by NASA to evaluate balance function of returning shuttle astronauts. Figure 2 shows a patient being trained on a Balance Master unit providing him with visual feedback about his limits of stability and balance function during therapy. Canalith Repositioning and Liberatory Maneuvers are used to treat Benign Paroxysmal Positional Vertigo (BPPV), the number one cause of vertigo in older adults. The diagnosis and treatment of these patients are dependent on the therapist's skill in understanding the patients eye movement associated with the condition that is termed nystagmus. Because of the transitory nature of the nystagmus that lasts less than 20 sec, the ability to capture the nystagmus on videotape is invaluable. This allows the therapist to review the tape and to

VESTIBULAR REHABILITATION/GANS 155 THERAPY MODELS Figure 2 Balance Master provides visual feedback for the patient's postural control training. document the efficacy of treatment. It is also an excellent teaching tool for patients, their families, and referring physicians. This technology is simple and requires only a TV/VCR to plug into for review and taping, as seen in Figure 3. It is important that clinicians make a differential diagnosis in BPPV, identifying the involved canal as well as the canalithiasis vs. cupulolithiasis variant. Figure 4 provides a simplified clinical pathway for diagnosis and treatment ofbppv. Self-Directed Exercises This is a homebased therapy that patients can do on their own. Each program is individually designed for patients (based on their test results) to include situations that bring on their symptoms. This approach is most commonly done with patients who do not require supervision while they exercise. Best results occur when the patient spends 20 to 30 min per session, 2 to 3 times daily. Most patients report a significant reduction in symptoms within a 2 to 4 week span. This has been a particularly valuable method for patients who have busy social or professional lives, and who cannot find the time (and are not required) to come into the clinic (see Table 5). Clinician-Directed Exercises This program is designed for patients whose symptoms may be rather severe and require supervision during the exercises. Therapy sessions usually include the use of a variety of special vestibular therapy equipment that most people thoroughly enjoy using. Fall prevention also is emphasized for Figure 3 Video-oculography provides clinicians with the ability to review and record eye movement.

156 SEMINARS IN HEARING/VOLUME 23, NUMBER 2 2002 f ' Negative Figure 4 Diagnostic and treatment clinical pathways for BPPV of the posterior and horizontal canal. older patients. Typically, the patient participates in one or two 60-min sessions per week, with an average of7 to 12 sessions. As the patient progresses, he/she is given some selfdirected exercises for use at home to accelerate improvement (see Table 6). CASE STUDY The following case study and clinical pathway is provided as an example of a typical vestibular patient. History and Symptoms A 49-year-old female was referred to the clinic by her primary care physician with a chief complaint of acute positional vertigo. The physician obtained a magnetic resonance image (MRI) and blood work profile, all of which were reported as normal. Her history included episodes of vertigo, the first of which began approximately four months prior. The initial episode lasted for approximately 7 to 8 days, with severe nausea and emesis throughout the episodic period. She enjoyed a spontaneous recovery of the Table 5 Self-Directed Vestibular Rehabilitation Therapy Ideal for high frequency UVDs without acute symptoms or imbalance. Minimizes disruption of work or home lifestyle. Cost effective, no need for third-party involvement. Requires motivated patient willing to perform protocols 2-3 times per day for 30 to 90 days. Treatment efficacy as successful as clinician directed. Table 6 Clinician-Directed Vestibular Rehabilitation Therapy Practical for patients with acute motion or visually provoked symptoms. Those who are unable to proceed without a coach present. Patients with UVDs with imbalance or unsteadiness. Therapy sessions 1-2 times per week for 6 weeks or less. Patients supplement therapy with home protocols.

VESTIBULAR REHABILITATION/GANS 157 vertigo and was symptom-free until approximately two months later. The second attack lasted about 7 to 8 days. The only other condition or symptom that occurred during these acute episodes was a significant outbreak of cold sores. Following the last attack (within 4 to 5 days), the patient reported an acute episode of vertigo when she would lie flat or turn her head while lying down. This vertigo would last only seconds. Her complaints also included a sensation that the world was "jiggling" when she looks from side-to-side or when walking. She felt as though her eyes "didn't have any shock absorbers." Although the sensation ofherworld bouncing is not as frightening as the acute positional vertigo, it is annoying and has limited her activity level. No hearing loss was associated with the attacks or subsequent to them, nor was there a history of migraine or migraine equivalent. Clinical Findings Video-Oculography revealed a left posterior canalithiasis during modified Hallpike positioning. A 43% left unilateral weakness was revealed on the caloric portion of VNG testing. Vestibular Autorotation Testing indicated abnormal (hypofunction) gain in the horizontal and vertical plane. Computerized Dynamic Visual Acuity Test (CD VAT) produced a 25% decrease in visual acuity with active head movement in the vertical plane. All other audiologic studies were unremarkable. The patient had normal hearing acuity for all test frequencies. Normal emission studies and distortion product otoacoustic emissions also were obtained. Recommendations The treatment strategy with this patient was twofold. First, the recurring attacks and nature of symptoms (including outbreak of cold sores) was suggestive of a viral vestibular neuritis. An otology consult was conducted. Following positive lab results for the herpes simplex type 1, the patient was placed on an antiviral medica- tion prescription and a daily regimen of a Lysine supplement by the otologist to control or inhibit further outbreaks. The patient was referred back to the clinic for treatment of the left posterior canal BPPV and noncompensated left UVD. Treatment and Outcomes As can be seen in the clinical pathways of Figure 5, the patient's VRT pathway included several visits. During visit one, the left posterior canal BPPV was treated with a modified Canalith Repositioning Maneuver. The patient was placed in a soft cervical collar to reduce head movement over the next 24 hours, and provided with written and verbal instructions. She was scheduled to return to the clinic for a second visit, at which time Video-Oculographic recording would be used to ensure that the BPPV had been cleared. If the patient's oscillopsia-type symptoms persisted, she would then be provided with a Self-Directed Vestibular Rehabilitation Program. On the second visit, the patient was deemed to have been successfully cleared of the BPPV based on the absence of rotatory-torsional nystagmus and vertigo with modified Hallpike positioning. There was no migration into any of the adjoining semicircular canals. She did report her oscillopsia-type complaint and the visual provoked symptoms (as when walking through the grocery store or through a mall) persisted. She was provided with a Self-Directed Vestibular Rehabilitation Program. On the third visit, which was 60 days post initiation of the program, she reported a 100% reduction in symptoms. Retesting ofvestibular Autorotation and Computerized Dynamic Visual Acuity Testing indicated a recovery and return to normal function on both tests. The patient was pleased with these results and was discharged from clinical care. She was encouraged to follow-up with both her primary care physician and the otologist should she have a recurrence of the acute-phase vestibular neuritis. She was encouraged to recom-

158 SEMINARS IN HEARING/VOLUME 23, NUMBER 2 2002 Figure 5 Diagnosis and treatment clinical pathway for case study of 49-year-old female with left posterior canal Benign Paroxysmal Positional Vertigo, and noncompensated left unilateral vestibular dysfunction, postvestibular neuritis. mence with her Self-Directed Vestibular Rehabilitation Protocols if at any time she felt a return of any of the oscillopsic symptoms with active head movement. SUMMARY Fifty years ofliterature, clinical experience, and a growing patient acceptance has solidified VRT as an important and efficacious nonmedical treatment for the symptoms of noncompensated vestibular disorders. Our understanding of the importance of intact VOR function in human equilibrium, and new and simplified tests of this system will allow us to continue to quickly identify and treat this population. New and exciting research in cochleovestibular hair cell regeneration may someday make VRT unnecessary. In the meantime, VRT presents as one of the most simple and successful treatment options available. ABBREVIATIONS BPPV Benign Paroxysmal Positioning Vertigo CDP Computerized Dynamic Posturography CDVAT Computerized Dynamic Visual CNS Acuity Test central nervous system CTSIB Clinical Test of Sensory Integration ofbalance MRI NIH VOR VRT VSR magnetic resonance image National Institutes of Health vestibula-ocular reflex Vestibular Rehabilitation Therapy vestibulo-spinal reflex

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